#include <bits/stdc++.h>
using namespace std;
#include <atcoder/scc>
using namespace atcoder;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
const int N = 2e5 + 5;

int n, m;
int a[N];

int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n >> m;
  scc_graph graph(n);
  rep(i, 1, m) {
    int u, v;
    cin >> u >> v;
    graph.add_edge(u, v);
  }
  vector<vector<int>> res = graph.scc();
  cout << res.size() << endl;
  for (const auto& c : res) {
    cout << c.size() << ' ';
    for (int v : c) cout << v << ' ';
    cout << endl;
  }
  return 0;
}